Some scientists think receding sea ice could lead to species mingling

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on Apr 26th, 2010 and filed under Animals.
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As long-term climate models predict declining amounts of sea ice in the Arctic, a University of Alaska Fairbanks researcher believes the change could bring an unexpected result — more inter-species breeding among mammals that live in the far north.

Brendan Kelly, a marine biology professor at UAF’s International Arctic Research Center, said the presence of sea ice has resulted in the isolation of numerous animals in the Arctic during the past 10,000 years or more. Those animals have evolved gradually into distinct species, such as walruses, ringed seals and polar bears.

But without ice to separate them in the future, Kelly believes many of those distant cousins will start to mingle again. The result could be more breeding between species, resulting in a biological stew that could reshape animal life in the Arctic.

“In 100 years, the species (in the Arctic) will be different than the species today,” Kelly said. “Is that good; is that bad? It’s different, for sure.”

Kelly discussed the theory during a teleconference hosted by the Alaska Center for Climate Assessment and Policy on Tuesday and has submitted a manuscript on the subject to Global Change Biology, a peer-reviewed science journal.

Kelly said there’s an understandable public weariness toward scientists who attribute every blip in the ecosystem to global warming but said he’s confident the theory is sound.

He said there are at least 28 mammal species that are likely candidates to interbreed. Among several of them, there’s already evidence it is happening.

In the past decade, a number of discoveries have been made in the north that appear to be offspring from two different species. They include an animal that looks like a blend of a harp seal and hooded seal, a ribbon seal-spotted seal hybrid, and a whale that resembles both a beluga and narwhal.

The phenomena also has been seen on land, where at least two grizzly-polar bear mixes have been found.

“This is probably going on more than we think. We just don’t see it,” Kelly said.

Although it seems unlikely that distinct species could create offspring together, Kelly said species classification is often subjective. There often isn’t a bright line between differing species, and some significantly different animals can mate and reproduce.

UAF Marine Biology Professor Mike Castellini agrees the likelihood of mixed-species breeding is growing in the far north. He said many uncertainties remain, but they’re underscored by a simple fact — Arctic animals are coming into contact with each other more than at any other time in the past 10,000 years.

“There are clearly more opportunities for these species to interact with each other on a number of levels,” he said.

The coverage area of summer sea ice in the Arctic has actually increased slightly in each of the last few years, although it remains about 25 percent below the 30-year average for the area, according to the National Oceanic and Atmospheric Administration. NOAA projects that the Arctic could be ice-free in the summer within 30 years.

Unfortunately, Kelly said the inter-species breeding probably won’t result in an evolutionary adaptation to the changing conditions.

Although gradual evolution is thought to be a key to long-term animal survival, Kelly said the rapid change in sea ice probably won’t give Arctic mammals enough time to adjust. He said the unfortunate result is likely to be a spike in extinction rates.